Prader Willi Syndrome is thought to affect 1 in every 15000 births. It is a rare, non-inherited genetic disorder where several genes on chromosome 15 are either deleted or not expressed. To date, there is no cure.
PWS affects the hypothalamus, the area of the brain responsible for regulating many of the body’s systems including metabolism, the development of muscle tone, regulating temperature control, blood pressure, heartbeat and sleep/wake cycles, the expression of emotions and many other body functions including controlling hunger. Due to this, a person with PWS exhibits low muscle tone, small statue, a slower metabolism, intellectual disabilities, anxiety and an insatiable appetite.
A Dietitian can play a significant role in a person with PWS’s life. PWS is the number 1 genetic cause of childhood obesity with issues with appetite being a component in PWS that significantly affects an individual and is quite contradictory in its presentation across their lifespan. There are 7 main stages of appetite in PWS (1).
- stage 0 - in utero, less growth in weight and length than their unaffected siblings
- stage 1a - from birth, no interest in feeding, may need to be tube fed
- stage 1b - feeding normalises and infant grows steadily along the growth curve
- stage 2a - weight increases without change in calorie intake
- stage 2b - weight gain associated with an increase interest in food
- stage 3 - hyperphagia, food seeking and lack of satiety (this generally occurs around 8yrs of age)
- stage 4 - rare cases of some adults no longer hyperphagic and are able to feel full
So what are the nutritional considerations for someone with PWS?
There is a high risk of obesity in individuals with PWS due to individuals having a slower metabolism, being placed on restrictive diets and who are preoccupied with or obsessive about food. In order to maintain a healthy weight once an individual becomes hyperphagic, an individual often requires dietary restriction of 50% of the estimated energy requirements for a person of the same age without PWS. In order to achieve this strict dietary regime, cupboards and fridges are typically locked to prevent anxiety and temptation around food and to keep the individual safe. A person with PWS could quickly consume a large volume of food resulting in choking or a perforation to the lining of the stomach which in severe cases can lead to death.
What is the current dietary advice for PWS?
There is no specific diet for PWS. Different dietary approaches work for different families. What is typically recommended however is to aim for a Mediterranean style diet that focuses on good quality lean proteins, healthy fats, fresh fruits and vegetables and complex carbohydrates.
The level of calorie restriction is very individualised with a ‘no one size fits all’ approach and although a reduced calorie diet is effective in controlling weight in children with PWS, studies have found that calorie restriction alone does not control the amount of body fat as well as a carbohydrate controlled diet (2). Research suggests that a calorie controlled diet providing ~45% carbohydrates, 30% fat and 25% protein with at least 20g fibre works best for weight control and improved body composition (2).
Sweet foods, sugar and sweeteners should be avoided in those with PWS. Apart from typically being higher calorie, nutrient poor foods, sweet foods when they hit our tongue, activate reward sensors in our brain signalling to want more and more. The sweet taste, whether it comes from natural sources or artificial sweeteners promotes an increased desire for sweet foods and this mechanism is more pronounced in those with PWS.
Micronutrient supplementation should be individualised and based off consultation with a doctor and dietitian. Depending on the type of diet the family follows will determine what vitamins and minerals may be of concern.
What are the common dietary management strategies?
Having a food and eating schedule can be particularly important for people with PWS as it helps the individual to understand that food will be offered at certain times and removes the uncertainty about what exactly will be offered. This helps to remove any DOUBT that food will be offered again and the HOPE (or chance) of getting more food that isn’t planned which helps to reduce stress and anxiety. Lastly, there will be no DISAPPOINTMENT as the child has received the food they could expect and at the time they were expecting (3).
Setting rules around eating such as only eating while seated at the table or only allowed to eat from their plate/lunch box can also help to establish positive behaviours. Never using food as a reward nor giving into tantrums are also ways in which some families manage this aspect of the condition. That being said, food should never be restricted as a form of punishment either nor should other family members eat “treat” foods or restricted foods in front of the family member who has PWS.
Exercise is another weight management strategy that should be encouraged from an early age. Physical activity is recommended for people with PWS as it improves mobility and prevents unwanted weight gain. A recent study (2019) found that long term (>6 months), consistent physical activity saw improvements in cardiovascular fitness, body weight and composition and glucose metabolism in adults with PWS and T2DM(4).
With the right support from medical professionals and having friends, family and other care givers on the same page as to what is best for the child, families can manage their child’s dietary pattern and weight and redefine their child’s future.
(1) Miller et al. (2011) Nutritional Phases in Prader-Willi Syndrome. Am J of Med Genet. 9999, 1-10
(2) Miller et al. (2013) A reduced-energy intake, well-balanced diet improves weight control in children with Prader-Willi syndrome. J Hum Nutr Diet. 26, 2-9
(3) New Concepts in Nutrition: PWS Nutrition Revised - Linda M. Goulash, MD, Pittsburgh Partnership, 2017
(4) Morales et al. (2019) Physical Exercise and Prader-Willi Syndrome: A systematic review. Clin Endo. 90, 649-661
PWS New Zealand, Dietary Management, www.pws.org.nz